Debris-flow generated tsunamis and their dependence on debris-flow dynamics
Debris-flow generated tsunamis and their dependence on debris-flow dynamics
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DOI：
10.1016/j.coastaleng.2019.103623
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发表时间：
2020-04
影响因子：
4.4
通讯作者：
S. I. Lange;N. Santa;S. Pudasaini;M. Kleinhans;T. Haas
中科院分区：
文献类型：
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作者：
S. I. Lange;N. Santa;S. Pudasaini;M. Kleinhans;T. Haas
泥石流引发的海啸对湖边的定居点和基础设施来说是极其危险的。泥石流成分强烈影响泥石流的厚度和速度，因此也产生海啸。然而，人们对这种相互作用知之甚少。本文通过一个由倾斜出流通道过渡到三维水库的小比例尺物理模型，研究了泥石流体积、成分（砾石、砂、粘土、水）和陆上出流坡度对波浪速度和振幅的影响，结果表明，泥石流在出流时，将水流向前推动，直到波浪速度超过水下泥石流速度（即弗劳德数<1）。然后，波从泥石流中分离出来，传播到远场。泥石流的推动使生成的波浪过陡并加速，超过了线性波浪理论对浅水波的预测。波高与泥石流流速的相关性最强。岩屑流速随着水和粘土含量的增加而增加（高达22%），这两者都润滑了流动。远场领先波振幅与泥石流动量（速度倍有效质量），这主要是一个函数的泥石流厚度，水和粘土container.We测试的适用性公布的（半经验）方程预测海啸振幅产生的干滑坡，并表明，他们在一定程度上也适用于泥石流。潜在的尺度效应，特别是考虑到最小的波浪和水深，可能会影响这些预测的适用性和翻译的结果，现场规模。我们的研究结果表明，海啸的产生和演变的泥石流组成的重要性，因此，包括预测模拟模型中的流动组成的必要性。
Debris-flow generated tsunamis can be extremely dangerous for lakeside settlements and infrastructure. Debris-flow composition strongly affects debris-flow thickness and velocity, and therefore also the generated tsunami. This interaction is, however, poorly understood. We investigate the effects of debris-flow volume, composition (gravel, sand, clay, water) and subaerial outflow slope on wave celerity and amplitude in a small-scale physical model consisting of an inclined outflow channel which transits into a three-dimensional water reservoir.We find that upon debouching, a debris flow pushes the water forward until wave celerity exceeds subaqueous debris-flow velocity (i.e. Froude number <1). The wave then detaches from the debris flow and travels into the far-field. Pushing of the debris-flow oversteepens and accelerates the generated wave beyond the celerity predicted by linear wave theory for shallow waves. It also increases its non-linearity but does not result in wave breaking.Wave celerity has the strongest relation with debris-flow velocity. Debris-flow velocity increases with increasing water and clay content (up to 22%), which both lubricate the flow. Far-field leading wave amplitude has the strongest relation with debris-flow momentum (velocity times effective mass), which is mostly a function of debris-flow thickness, water and clay content.We test the applicability of published (semi-empirical) equations for predicting tsunami amplitude generated by dry landslides, and show that they are to some extent also applicable to debris flow. Potential scale effects, especially considering the smallest waves and water depths, could influence the applicability of these predictors and translation of the results to the field scale. Our results demonstrate the importance of debris-flow composition on tsunami generation and evolution, and thus the necessity of including flow composition in predictive simulation models.